• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.812-818
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• 2009

A MOV(Main Oxidizer shutoff Valve) controls the flow rate of liquid oxygen into the rocket combustor by opening and shutting operations piloted by a pneumatic force. In order to improve the effective design for sealing parts of poppet and piston assemblies, the poppet assembly has been designed to be just contacted with the piston assembly. However, to avoid a gap at the poppet/piston contact surface and to evaluate the MOV operating performance, an analyze on the force balance during the closing motion have been performed. For the accuracy of the analysis, the friction forces and the hydraulic forces have been respectively obtained by experiments and CFD analysis. Through the analysis, some important design parameters such as the spring constant, poppet friction and orifice size in the force balance have been introduced and the required operation performance of the MOV has been proved feasible.

• Journal of Astronomy and Space Sciences
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• v.26 no.3
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• pp.403-416
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• 2009

COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and developed by KARl for communication, ocean and meteorological observations. It will be tested under vacuum and very low temperature conditions in order to verify thermal design of COMS. The test will be performed by using KARI large thermal vacuum chamber, which was developed by KARI, and the COMS will be the first flight satellite tested in this chamber. The purposes of thermal balance test are to correlate analytical model used for design evaluation and predicting temperatures, and to verify and adjust thermal control concept. KARI has plan to use heating plates to simulate space hot condition especially for radiator panels of satellite such as north and south panels. They will be controlled from 90 K to 273 K by circulating GN2 and LN2 alternatively according to the test phases, while the main shroud of the vacuum chamber will be under constant temperature, 90 K, during all thermal balance test. This paper presents thermal modelling including test chamber, heating plates and the satellite without solar array wing and Ka-band reflectors and discusses temperature prediction during thermal balance test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.648-651
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• 2004

Biped robot has better mobility than other mobile robot, but it is hard to maintain balance during walking. In order to maintain balance, stability analysis is a key point for a biped robot. The zero moment point analysis has been used most in stability analysis. In this paper, we propose different method of stability analysis using wrench system. It is possible to generate a wrench system by applying a force along an axis in space and simultaneously applying a moment about the same axis. Wrench system is equivalent to a force and moment applied along the same axis. We compare the result of wrench system analysis with that of zero moment analysis in biped robot stability using simulation program.

• Journal of Power Electronics
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• v.19 no.1
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• pp.99-107
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• 2019

This study proposes a new modulation strategy to deal with unbalanced output voltage that is based on three-level neutral-point-clamped cascaded rectifiers. The fundament idea is to reallocate the value of the voltage levels generated by each of the modules on the basis of space vector pulse width modulation. This proposed modulation strategy can reduce the switching frequency while maintaining the mutual-module voltage balance. First, an analysis of unbalanced output voltage is reflected. Then a new modulation strategy is introduced in detail. Internal module capacitor voltages are balanced by the selection of redundant vectors. Moreover, the voltage balance ability is calculated. Finally, the feasibility of this modulation strategy is verified through experimental results.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.41.1-41.1
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• 2010

A bipolar magnetic field perturbation in the meridional plane was observed when the Polar spacecraft crossed the plasmapause near the midnight, which was identified by a clear jump in density and temperature, from the plasmasheet to the plasmasphere. The bipolar variation shows a negative-then-positive polarity. To examine the bipolar magnetic field perturbation at the plasmapause, we assume one-dimensional model with physical quantities varying along a direction normal to the plasmapause and employ two-fluid approach for the tangential plasmapause. That is, the magnetic fields on both sides are parallel. Considering Ampere's law and pressure balance relation, we have a perturbed magnetic field, which is consistent with the observation at the plasmapause.

• Journal of the Korean Institute of Landscape Architecture
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• v.44 no.5
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• pp.81-91
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• 2016

The study shows solutions of long-term unexecuted urban park and activation plans to facilitate the business promotion of Private Park Developers. This study conducted a feasibility analysis to determine if the business of a special case is applicable. The result of this study is as follows about three long-term unexecuted urban parks in Gwangju Metropolitan City's City Park. First, the three long-term unexecuted urban parks in Gwangju Metropolitan City's City Park are the forest type Neighborhood Parks. Businesses of a special case's park developing cost(average 0.4%) have a relatively low percentage. It is most affected by Land Compensation(average 33.8%) and building construction expenses(average 59.1%). Second, long-term unexecuted urban parks' Land Compensation and building construction expenses seed capital are excessive. The Bongsan Park balance floor space index is 179 percent; a reasonable profit floor space index is 220 percent. The Mareuk Park balance floor space index is 351 percent; a reasonable profit floor space index is 420 percent. The Jungoe Park balance floor space index is 327 percent; a reasonable profit floor space index is 400 percent. Third, to facilitate the business of special cases in deliberating, Bongsan Park should change its second class general residential area. Jungoe Park must change the quasi-residential area and semi-residential area. Mareuk Park must change the general commercial area. In this way, the feasibility of promoting private park projects will be improved.

• Journal of architectural history
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• v.5 no.1 s.9
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• pp.73-86
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• 1996

This study is to analyze the geometrical composition system for the plan of S. Pietro by Michelangelo. In the result of study, the plan is based on the geometrical elements of circle square cross, and shaped to symbolize the Universe which consists of the Heaven the Earth the Man. The plan is constituted of the conception of composition into hierarchy and repetition intersecting 45 degree the same sized square with inscribed square in a circle. Such the geometrical composition system can be found out a large number of example to the geometrical composition of architecture and city planning from Vitruvius to Bramante and Da Vinci. This plan is disposed in balance as the regularly proportional system of 1:1, 1:2, 1:3, which is formed the principal space. And the interior space is constituted of the organic space system, expanding to the direction of horizontal, vertical(ascension), development for primary space and secondary space with center in the geometric composition system of altar.

• Journal of Astronomy and Space Sciences
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• v.17 no.1
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• pp.99-106
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• 2000

When a deployed probe is biased by a high positive potential during a space experiment, the payload is induced to a negative voltage in order to balance the total current in the whole system. The return currents are due to the responding ions and secondary electrons on the payload surface. In order to understand the current collection mechanism, the process was simulated with a combination of resistor, inductor, and capacitor in SPICE program which was equivalent to the background plasma sheath. The simulation results were compared with experimental results from SPEAR-3 (Space Power Experiment Aboard Rocket-3). The return current curve in the simulation was compatible to the experimental result, and the simulation helped to predict the transient plasma response to a high voltage during the plasma sheath formation.

• Journal of Information Technology Applications and Management
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• v.20 no.1
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• pp.43-51
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• 2013

Human being does work to live out and they have their private life because human has sociality. Both work and life are important to live out but they are on the trade-off relationship. Because keeping the balance between work and life is too hard, it has been interested by academic and practical areas. Definition of Work-life balance here is that balance or imbalance arising between work and life has no negative impact on their daily life. Above all, Work-life balance is important because it is strongly related to identity. Recently, the introduction of the mobile office system has emerged as a way to solve the problem of work-life balance. It is based on the teleworking which was formerly generated. Teleworking is to perform the work in the employee's home or office space set aside without going into the workplace. Concept of the mobile office system here is not only using portable devices during work for convenience but also the system which is designed for the performance. Thanks to the diffusion of smart devices(smart phone, tablet pc), mobile office system has been spread. Although the importance of mobile office systems is emerging, there are few researches about it. Even they mostly focus on the standpoint of performance of mobile office system. However, Quality of life is as important as the performance. As a part of Quality of Life field, Work-life balance is the closest to employee's quality of life. So this study aims to examine the effect of the use of mobile office systems on work-life balance. To do so, we try to find factors effecting Work-life balance from existing studies and then set a research model. We set the use of mobile office systems as independent variables which are divided by use of function, use by location and use by situation. There are four dependent variables - sense of self command, sense of balance, solving work problem, solving life problem. We collected data from employees who are using mobile office systems on their job. 215 people were participated in the survey and we used multiple regression analysis to verify our research model. Results show that every independent variable has no impact on solving work problem while they have slight impact on the other dependent variables. Especially use on the business trip has significant effect on dependent variables. It means that there is a possibility use of mobile office system could control the employee's quality of life and system should be evolved until it covers even critical tasks. Also, support for mobile office system -education, encouragement-should be provided. By mobile office system is maturing, future research would be done.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11C
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• pp.1040-1048
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• 2009

This paper proposes an auto flesh tone balance algorithm for the picture that is taken for people. General white balance algorithms bring neutral region into focus. But, other objects can be basis if its spectral reflectance is known. In this paper the basis for white balance is human face. For experiment, first, transfer characteristic of image sensor is analyzed and camera output RGB on average face chromaticity under standard illumination is calculated. Second, Output rate for the image is adjusted to make RGB rate for the face photo area taken under unknown illumination RGB rate that is already calculated. Input tri-stimulus XYZ can be calculated from camera output RGB by camera transfer matrix. And input tri-stimulus XYZ is transformed to standard color space (sRGB) using sRGB transfer matrix. For display, RGB data is encoded as eight-bit data after gamma correction. Algorithm is applied to average face color that is light skin color of Macbeth color chart and average color of various face colors that are actually measured.